Tag Archives: Gas Mixing & Blending

Talking Biogas Production In Europe

Europe is quickly becoming a hotspot for the biogas industry, and Sierra and our local French distributor Alto Instruments took advantage of that fact by exhibiting at BiogazEurope in France. Attendees learned about the entire biomass process, from the bio side of things (mass) to the energy side (electricity).

Some trending applications featured at the show included:

  • Biomass digesting
  • Optimizing/upgrading biomass
  • Precise flow measurementSierra-Alto Booth at BiogazEurope 2014

Overall,  trend was the need for high-accuracy flow meter measurement throughout the whole biogas process to optimize production and bring efficiency while creating electricity (energy) from fossil fuels.

To really monetize biogas and create the most efficient fuel sources, you must accurately measure how much biogas is produced in each stage of the process. Although biogas flow measurement is a challenging—mainly due to changing gas composition, low pressure, and dirty, wet gas—it’s not impossible. Which is why we featured our QuadraTherm 640i at the BiogazEurope show.

The 640i meets the criteria for successful biogas measurement by managing changes in:

  • Gas composition
  • Gas mass flow rate
  • Gas temperature
  • Gas pressure
  • Outside temperature
  • Pipe conditions (size and roughness)
  • Flow profile

These common fluctuating conditions inherent in biogas production can all be managed with accurate readings (the 640i maintains accuracy at +/- 0.75% of reading above 50% of full scale), without sending the flow meter back to the factory for recalibration. Who doesn’t want to reduce downtime and save money?

For more information on precise biogas flow measurement, download our white paper.

Flow Tip Video: Learn Why Ease-of-Use is Critical for Flow Meter Selection

Many times scientists and researchers spend more time setting up equipment and instrumentation for their experiments than conducting actual experiments to gather important data. This holds true for flow meters and controllers to measure and control gases to experiments. Some flow meters are very cumbersome with no display, can only measure one gas, low value for price, and limited application flexibility.  And if you need application flexibility and ease-of-use, many times the price of the mass flow meter for these “add-ons” drastically increases.

Over a decade ago, when designing Sierra’s SmartTrak 100 mass flow meters and controllers, our engineers realized the importance of designing a “standard model” flow meter that was fully loaded with easy-to-use features and the ability to quickly change flow meter parameters as the experiment changes.  Jim Oswald, Sierra’s Technical Support Supervisor, gives us an insider’s view of how easy SmartTrak mass flow meters and controllers are to use in the latest Flow Tip Video.

5 Reasons Why the SmartTrak is Easy-to-Use Even When Experimentation Conditions Change

  1. First of all, because of the illuminated LCD backlit display, which has been standard on the SmartTrak for over a decade, scientists can easily see the flow meter’s readout from many angles and change data easily through a push-button menu. The backlit display also has low power consumption.
  2. Many times in experiments, application conditions change like flow rate, gas, or configuration. If your gas changes, you can quickly choose from 10 preprogrammed gases with our Dial-a-Gas feature through the onboard push-button display or remote pilot module, which is essentially a “remote” display/interface for adjustment to challenging experimentation configurations. Simply choose a new gas from the menu and it’s ready to go, without losing any accuracy. You can also adjust engineering units, flow range, and set zero, span and full scale independently for each gas.
  3. For easy integration with your system or experiment, add a plug-in Compod which turns the SmartTrak into a mini PLC–no additional computers needed. The Compod module replaces a touchpad and allows you to communicate not only with one, but with over 200 SmartTrak units if you install a multi-drop. You can add functionality to control a positive shutoff valve, add a pulse output, and read and react to a pressure transmitter.
  4. Free user software and a variety of communications protocols like Modbus, Profibus and Foundation Fieldbus, make every SmartTrak easy to integrate into your digital communications network.
  5. Accurate and repeatable data regardless of changes in application parameters make experimenting easier–no repeating experiments due to unreliable flow data. SmartTrak’s NIST traceable accuracy is backed by our ten-point primary standard calibration over the entire flow range.

Learn more about the SmartTrak Series or download the Infographic.

Chemical Engineering Magazine Article By Sierra’s Founder

Chemical Engineering Flow Meters

Sierra’s Founder, Dr. John G. Olin, looks at the Principles of Operation, Installation, Calibration and Best Applications for Thermal Mass Flow Meters…

Read the full article in Chemical Engineering Magazine.

How to Supercharge the SmartTrak Mass Flow Controller with Compod

smarttrak-compod_highStreamline, simplify and save time and money by plugging the innovative Compod upgrade into the face of any SmartTrak 100 mass flow meter or controller. SmartTrak is not only a true multi-gas digital mass flow controller, it can control your process too.

If you need more functionality to control a positive shutoff valve, have a pulse output, or read a pressure transmitter, that is no problem with Compod. It is also programmable by the user. Set up simple process control systems driven by SmartTrak without the need for PLCs or computers.

Daisy chain multiple mass flow controllers to network multiple instruments using open-source fully network-enabled multi-drop RS-485 / Modbus RTU. Upgrading your SmartTrak MFC with Compod adds two digital output channels and one analog input channel and a configurable pulse output channel to allow functions of much more complex systems at a fraction of the cost.


Compod acts as a vital link in your more complex process control network. It monitors the operation of instruments and provides potential problem alerts. Send and receive data and even perform data logging and diagnostics that notify users of valve faults or system upsets.

Compod is available with a local LCD display for local monitoring and flow totalization and can be used with new instruments or added to existing models.  Sierra provides free Compod software or you can write your own using open-source MODBUS protocol.

Watch Video “>SmartTrak 100, Master of ALL Flows!

Common applications include:

Compod really puts the “smart” in your SmartTrak mass flow controller. Learn more about Compod and the SmartTrak series.

Best Practices for Mass Flow Controller Selection & Installation

Mass Flow Controller Best PracticesAs scientists, facilities managers and manufacturing engineers, specifying equipment is a part of our daily work life. What product do I need? What’s the best price for the value? How do I install the product once I get it? The more information about best practice principles, the easier the job is of specifying and buying equipment. Through our years of experience of specifying, installing, and servicing mass flow controllers, we have compiled a comprehensive list of best practices by users for the selection, safety, installation, and operation of their thermal mass flow meters and controllers are as follows:

Best Practices-Product Selection
1. Select only those mass flow meters and flow controllers where the manufacturer’s specifications meet the conditions of the application, such as maximum and minimum flow rate, pressure and temperature. Some manufacturers have software programs that recommend the instrument model best suited for your application.

2. To minimize pressure drop and flow non-uniformities, you should select the instrument with the largest inlet fittings compatible with the size of the process line. In the case of corrosive gases, the instrument selected should have materials of construction that provide protection against corrosion.

3. Size the instrument so it operates in the upper two-thirds of its full scale mass flow rate range.

Installation and Set-Up

4. Install the instrument only in process lines that meet the manufacture’s pressure and temperature ratings. A margin of safety should be provided if spikes and surges exist in the process. Proper pressure relief valves and burst plates should be installed in high pressure applications.

5. To avoid obstructions in the sensor tube and the narrow flow channels in the laminar flow element, you should install the instrument in process lines that have clean gases. Upstream particulate filters properly sized for the flow rate, with a minimum rating of 5 microns are recommended for all applications.

6. To avoid thermal siphoning (or, the so-called, “chimney effect”), you should install the instrument in the process line with the axis of the flow body oriented horizontally, not vertically. At zero flow, if the axis is vertical, the gas heated by the sensor tube rises upward through the sensor tube and creates a closed flow loop in the flow body that causes the instrument to read a flow rate when there is none. This effect is significant only in the very lowest portion of the full scale range. If system constraints require vertical mounting, then the instrument should be re-zeroed in the field. Vertical mounting requirements should be communicated to the manufacturer upon order so the instrument can be adjusted to meet these special requirements.

7. To avoid stress on the springs in the control valve, particularly in medium- and high-flow mass flow controllers, you should install the instrument in the process line with the axis of the flow body oriented horizontally as required above and, additionally, with the control valve located on top of the flow body, not on the bottom or the side. If system constraints require a different instrument orientation, you should communicate this requirement to the manufacturer upon order so that adjustments can be made.

8. After turning on the instrument, you should allow the instrument to warm up for the time period specified by the manufacturer. A warm-up time of about 10 to 30 minutes typically is required for the instrument to reach full accuracy.

9. Be sure to zero your mass flow meters and controllers prior to first use and periodically afterward on a schedule based on the manufacturer’s recommendations or your own experience. The zero flow output signal should be averaged over a sufficient time interval. Preferably, zeroing should be performed with the actual gas to be measured at the same pressure and temperature of the application, or close to it. If there is a change of gas, the instrument should be flushed with the new gas before being zeroed. Obviously, for proper zeroing, the flow rate must be zero. This is best accomplished, in the case of controllers, by commanding the control valve to be shut, and, in the case of both mass flow meters and controllers, by closing shut-off valves installed just upstream and downstream of the instrument. In the absence of these valves, the process line must have other means to insure that the flow is zero.

Following these best practices are sure to result in the most accurate measurement outcome with your new mass flow meter or controller. Have any other tips we didn’t mention or questions about mass flow control? Please leave them in the comments section below.

Complete Guide to Gas Mixing and Blending | Sierra Instruments


Gas mixing sounds simple enough. You simply mix a number of pure gasses to create a new mixture. Unfortunately, it’s not usually as simple as it sounds. There are many variables and factors that play a role. 

In this post, we’ll dissect this challenging application and discuss how to obtain perfect gas mixing and blending with capillary thermal mass flow controller technology.

Why It’s Important

There are many applications and industries that rely on gas mixing and blending. In a laboratory environment, our customers need gas mixtures to test catalysts to see the effect of certain concentrations of pollutants on gasses. The food industry needs a mixture of gasses to prevent oxidation of food. The semiconductor industry needs accurate gas mixing to generate certain atmospheres in their ovens. Hospitals mix gases to create O2 rich air or narcotic gasses. 

There are hundreds of other applications that utilize gas mixing like welding, dilution, chemical reactions, testing of gas analyzers, filling light bulbs, and double glazing windows.  The most common gas blending applications, however, are related to burning and combustion.

Do you remember the basics of combustion? You need fuel, oxygen, and ignition. If the fuel and the oxygen are both gasses, it is ideal to mix them in the perfect ratio to get optimum and clean combustion. 

We can name several applications for this type of gas mixing: Your car, big boilers, small flames used in the glass industry, big power plants, Waste burning plants, etc.

Why Mass Flow Meters?

In gas mixing and blending, direct gas mass flow control provided by a mass flow controller (MFC) not volumetric flow control, is very important. Proper mixing and blending saves money and increases repeatability of the end product and improves quality.

Combustion or burning applications have their own set of challenges. Combustion or burning is a chemical process, a reaction between molecules. To quantify the gas used, then, we should count those gas molecules and not the space between these gas molecules. We do that by measuring the gas mass flow, the weight of the gas (molecules), and not the volume (molecules + space between molecules).

The nice thing about Mass Flow Controllers is that they do just that: They measure and/or control the gas mass flow. They are molecule counters! 

Accuracy in Gas Mixing & Blending

Mass flow controllers are devices that have an accuracy of % of full scale (%FS). That means that the uncertainty of a 1% device is 1% of the maximum flow range of the instrument.

For example, if you purchase a mass flow controller with a range of 0-500 SLPM and the unit has an uncertainty 1% of full scale, the uncertainty is 1% of 500 = 5 SLPM. So, when you control a mass flow rate of 500 SLPM, the flow can be between 495 to 505 SLPM. However, if you control mass flow rate at 10 SLPM using the same 500 SLPM instrument, the uncertainty is still +/-5 SLPM.  As a result, the controlled flow could be anywhere between 5 SLPM up to 15 SLPM. Pretty bad!

The good news is that the newest generation of high-performance Thermal Mass Flow Controllers has drastically improved with the aid of advanced electronics, sensor, and laminar flow element design and linearization mathematics are getting closer to being % of measured value devices. And for a gas mixing and blending application requiring multiple mass flow controllers, the price of the instrument matters.

You’re probably wondering what all this means for gas mixing and blending applications? The lesson learned is that the absolute accuracy is not as good when you operate the mass flow controller at the bottom of the maximum flow range of the instrument, so size your instrument correctly. 

This sizing of mass flow controllers in a gas mixing system is critical. You should be very clear what the purpose and the operational range of each mass flow controller in your gas mix system should be. Ask the manufacturer of the instrument to assist you as they probably have many customers faced with the same challenge.

‘Kwik Kalucations’ with K-Factors

‘Kwik Kalucations’ with K-factors make gas mixing with a single gas mass flow meter simple.

If you’re looking to improve flexibility and save money when it comes to gas mixing and blending applications, consider applying a “K-Factor.” A dimensionless numerical relation of a specific gas vs. air or nitrogen, a gas K-factor never changes. If K-factors will work in your application, you can use one gas mass flow controller calibrated on air or nitrogen for several gasses by simply applying the K-factor.

K-factors, in general, do not change and are used for measurement and control of mass flow rate in units of SCCM and SLPM.  For example, if you calibrate your capillary-sensor gas mass flow controller with air for 0-100 SLPM, but intend to run 100 SLPM of argon through it, you will only get an output of 69 SLPM for the instrument. That’s because the physical properties of argon that affect heat transfer (the standard gas density and specific heat) are different than air.

Furthermore, when you run enough argon through the instrument so that it indicates 100 SLPM, you will actually find the flow of argon is 145 SLPM. Thus, the K-factor of Argon is always 145/100 = 1.45.

Every gas has its own K-factor, but there can be slight differences across various brands of instruments. Is the K-factor a perfect linear function? Well, we assume so, but in reality that is not always true, especially with lower-cost flow sensors and flow meters for gas on the market today. Errors can be up to 7% on very specific light gasses like hydrogen or helium for these lower performing instruments. 

In contrast, the SmartTrak 100 digital mass flow controller is a premium instrument with a high level of reliability with K-factor behavior enabling such technologies as Dial-A-Gas, multi-gas capability. This makes the SmartTrak 100, together with the advanced digital communication possibilities of the Compod, an ideal choice in gas mixing and blending applications.

Dilution in Gas Mixing

Dilution is a special application in the world of gas mixing. Basically, you are diluting a concentration of gas in an already existing gas mixture. Let’s say you have a gas mixture of 10% Ar / 90% N2 and you really need 5 Ar / 95% N2 for your application. The solution is to add more N2 to the mix, but how much? 

To answer the question of ‘how much,’ we first need to know if the gas mix ratio is in % mass or % volume. Let’s assume it is % mass. In that case, we need to generate a new mix of 50% of the original 10% Ar / 90% N2 mix and dilute (or mix in) that with 50% N2. The result is a new mix of 5% Ar / 95% N2 mix.

Most concentrations, however, are much smaller, more in the 0.0001% region. In general, one expresses this in ppm values (ppm = parts per million). This means that 10000 ppm = 1%.

Wouldn’t it be nice to have an automated gas mix system that calculates this all for you? Sierra can provide this for you, contact us to learn more about our SmartTrak® 100 Digital Mass Flow Controllers for Gas Mixing & Blending

Benefits of Capillary Thermal Mass Flow Controllers

  • Direct mass flow with +/- 0.5 percent full-scale accuracy
  • Patented, inherently linear laminar flow element design
  • Mass flow rates up to 1,000 slpm and down to 0 to 0.1 sccm
  • Pressure to 5,000 psig (345 barg) with low pressure drop of 4.5 psid (310 mBard)
  • Provides smooth and flexible valve performance, even at low flows
  • True multigas digital mass flow controller—up to 10 pre-programmed gases
  • 10-point NIST calibration on primary standard


Watch this video to learn more about SmartTrak®: Master of All Flows.

Ultra-High Pressure 5000 psig (345 barg) Gas Mass Flow Control…No Easy Task!

Overall, Sierra wants better accuracy and control of high pressure gas mass flows across industry in general, leading to better efficiency, and vastly reducing gas losses to save time and money for our customers.  But, how is it possible to accurately measure and control gas mass flow rates at pressures up to 5000 psig (345 barg)?

This is certainly no easy task. In fact, there are only a handful of mass flow meter and controller manufacturers who compete in this ultra-high pressure space due to the inherent challenges of this application. Sierra is proud to be a part of this elite group to manufacture ultra-high pressure flow meters and controllers.  Our solution is the SmartTrak 100HP. 100.HP.screen.capture.9.17.14

To embark on this ultra-high pressure journey, we have been pushed to add robust features to the mechanical design of our flagship SmartTrak 100 series and build an in house high-pressure flow calibration facility. Here are a few critical questions that needed to be answered to make our 100HP such a success.

Q: What is the market need for high pressure mass flow meters and controllers?  

A: There are a great number of potential applications requiring measurement and control of high pressure flows. It’s an ever-increasing market. When storing and transporting large amounts of gas, it is generally compressed to allow for greater ease in transport. Using the 100HP to control gas directly from the container it was shipped in, will yield greater accuracy and eliminate costly gas losses associated with inaccurate control.

Another application the 100HP is perfectly suited for is in the construction of pilot plants from a variety of industries. These much smaller, scaled down pilot plants operate under higher pressures than the intended application in order to increase the rate of chemical interactions to better match what the full-sized plant will experience. In many locations, the atmospheric composition of the air varies greatly from day to day. To eliminate this variation, many companies will re-create atmospheric air, directly from high-pressure gas cylinders. The 100HP provides high accuracy mass flow control of this gas, which allows both accurate and consistent air compositions that would otherwise be impossible.

Q: What separates Sierra’s high pressure mass flow controllers and meters in the market?

A: Because high pressure is an emerging market, the product lines of high pressure controllers and meters are similarly young. Our 100HP builds off of the proven and highly developed 100 Series product line that has been one of the most popular units at Sierra for over a decade. We’ve beefed up the mechanical features of our existing 100 product line to withstand far greater pressures, while leaving the working designs from the 100 series alone. This assures precision high performance as we build upon an existing proven core technology platform.

100.accumulator.v.2.Q: What was the inspiration for building our own high pressure flow calibration facility?  What advantages does that give Sierra owning their own high pressure calibration system?

A: Having our own facility assures shortened lead times and impeccable quality.  Our inspiration to build a high pressure calibration facility was mainly based on demand. Every month Sierra would gets inquiries for meters and controllers operating at pressures that are extremely challenging to match for calibration. We performed calculations and were confident that our existing flow-body could withstand the elevated pressures. Logically, the next step was to build a flow calibration facility and that’s exactly what we did.

The advantages to having an in-house high pressure flow calibration facility are innumerable. Primarily it allows us to offer meters and controllers that are rated to far greater pressures than before. It allows us to promise and deliver on a level of cleanliness that wouldn’t be possible if the facility wasn’t under our roof or control. It allows us to experiment and further develop the product line, because we can generate and ‘play’ with these high pressures.

Q: What does the future look like for Sierra’s high pressure line?  Your vision?

A: After assuring high quality of gas mass flow measurement and control, the vision for Sierra’s high pressure product line is to lead the market in ease-of use, accuracy, control, and price. By doing so, my hope is that customers will either begin using or convert to using Sierra’s 100 HP mass flow controllers and meters for all their high pressure gas control needs. Overall, Sierra wants better accuracy and control of high pressure gas flows across industry in general, leading to better efficiency, and vastly reducing gas losses to save time and money for our customers.  Let us know your high-pressure flow metering or control application challenges.

Check-out our SmartTrak 100HP product!

New From Sierra, MEMS-based Thermal MFC’s Set the Long-Term Stability Bar – High!


We have been in the capillary thermal mass flow business for nearly 45 years, many have asked us why we recently introduced MEMS thermal mass flow controllers into our product offering.  Combining superior physics, high reliability, and unparalleled flexibility, our new Sierra MEMS-based RedySmart brand mass flow controllers complement our Sierra Capillary-based SmartTrak brand mass flow controllers.

Unparalleled Stability









Our RedySmart MFC targets the Biopharm industry where historically, Sierra did not have a product with a perfect fit.  Biopharm OEMs appreciate the modularity, compact size, and price of the RedySmart MFC.  The incredible long term stability is probably the biggest factor.  Making a big statement in the industry, all Sierra MEMS devices, including RedySmart and RedyCompact, come with a Lifetime No-Drift Sensor Warranty for long-term peace of mind for end-users that will rely on these devices for top results.  Sierra is the only company in the industry to stand behind MFC sensor stability claims with a warranty.  Stability is made possible by state-of-the-art high-precision MEMS (Micro-Electro Mechanical Systems) technology utilizing an advanced CMOS  (Complementary Metal Oxide Semiconductor) sensor architecture.











50x Magnification of Redy MEMS Sensor

RedySmart thermal mass flow devices contain no moving parts and are unaffected by upstream temperature and pressure fluctuations, resulting in exceptional accuracy and repeatability.   With a compact footprint, easy integration onto a cost-effective multi-device gas mixing blocks, and a wide array of communications protocols, Sierra can now produce a gas mass flow meter or controller to meet nearly any requirement.

If gas composition changes, field-adjust to maintain flow meter accuracy?

Changes in gas composition cut into productivity in the field, exactly when you need accuracy in flow meter measurement the most. But what if you could retain that precision, even when those changes occur? Now you can do just that with qMix Software.  If your gas composition changes over time, you can now quickly field-adjust the QuadraTherm thermal mass flow meter. You avoid the expense of sending the instrument back to the factory for recalibration by reprogramming it in the field to assure optimum accuracy.

We’re committed to driving innovation here at Sierra, and our qMix Software plays a critical role in our flow meter solutions for the biogas and oil & gas industries. No more sending your air mass flow meter back to the factory for gas recalibration every time your gas changes. Talk about a productivity boost!

Benefits of Changing Gas Mixtures in the Field

qMix Flow Meter SoftwareTraditionally, thermal mass flow meters are calibrated using the exact gas mixture they are intended to measure, or a surrogate mixture with very similar properties. In many industrial applications, like biogas measurement, the gas composition changes from the original calibration. When changes in gas composition occur in the field, the accuracy of the flow meter is adversely affected.

In the past, the only way to correct for a change in gas composition was to return the meter to the factory for gas recalibration. qMix provides a dynamic solution to this problem by allowing end users to manage gas composition changes in the field right from the Smart Interface Program (SIP) provided free with every instrument.

Watch the video to find out more about qMix functionality.

Through an easy-to-use software interface, qMix allows you to:

  • Field-adjust and maintain flow meter accuracy if gas composition changes
  • Avoid costly recalibration; once qMix has been installed, no need to send unit back to the factory if gas composition changes
  • Create and upload unlimited gas mixtures onto one meter-free of charge
  • Save custom gas mixtures onto your personal “My Gases Database” for later use
  • Benefit from Sierra’s proprietary, ever-improving “Gas Database” to download more accurate gases

The qMix software package ships with every QuadraTherm 640i/780i on a beta trial basis as part of each meter’s SIP.


Top Blogs of 2020

Even though 2020 has come and gone, we would like to take a minute to recognize our Top Blogs from 2020.  As with most things in 2020, the theme of  “get back to the basics” resonated with our readers.

The winning blogs of 2020 all answered foundational questions like: “How does this work?” or “How do I do this?” Enjoy getting back to the flow basics.

Top Blogs of 2020 – Answering Your Top Questions

  1. What Is a Flow Rate Totalizer & How Does It Work?
    Discover how to correctly use flow meter totalizers and understand the power of the iSeries flow meter totalizer in the number one read blog of 2020.
  2. How do Ultrasonic Flow Meters Work?
    Get an in-depth understanding of how ultrasonic flow meters work and why you might choose one for your application.
  3. How a Vortex Flow Meter Works?
    This blog gives explains how vortex flow meters work and the various vortex sensor technology available for steam flow measurement.
  4. Tips & Tricks to Installing Your Flow Energy Meter
    Get practical hands-on advice on how to properly install your flow energy flow meters in this blog. To get an accurate measurement, proper installation is key. Most of the time when your flow meter “doesn’t work,” it could be that your flow meter is not installed properly.
  5. How do Water Flow Meters work?
    One of the most common applications and biggest markets out there is water measurement so it’s no wonder that our blog on how water flow meters work was a top read. Discover the four types of flow meter technologies for water applications and how they work today.
  6. How to obtain perfect gas mixing and blending?
    Offering a complete Guide to Gas Mixing and Blending, this blog dissects this challenging application and discusses how to obtain perfect gas mixing and blending with capillary thermal mass flow controller technology.
  7. Why mass flow instead of volumetric flow?
    Watch this quick tip-video blog to find out the difference between direct mass flow and volumetric flow technology and discover the advantages of direct mass flow.

More To Come In 2021

In 2021, you can expect in-depth content from Sierra Instruments that focuses on “how-to” content to achieve accurate flow measurement, increase energy efficiency, and save money on energy costs.

Welcome to 2021! Let’s make it an amazing year.